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HEATINC VENTILATING AIR CONDITIONING CUIDE 1944 Table 4. Solar Radiation'(Direct plus Sky) Impinging Against Walls Having Several Orientations and a Horizontal Surface For 40 Deg North Latitude on August 1 Sun Time 4:50 5:00 6:00 7:00 8:00 9:00 '10:00 11:00 12:00 1:00 2:00 3.-00 4:00 5KX) 6.-00 7.-00 7:10 Northeast 0 49 123 137 102 54 28 26 25.5 23.5 21 17 11 4.5 2.5 0 Intensity of Solas Radiation. Btu per Sq Ft pee Hour East 0 6 56 162 211, 195 152 94 26 25.5 23.5 21 17 11 4.5 2.5 0 Southeast 0 4 32 109 166 181 171 144 98 41 23.5 21 17 11 4.5 2.5 0 South 0 2.5 4.5 11 29 74 103 124 128 124 103 74 29 11 4.5 2.5 0 Southwest West 0 2.5 4.5 11 17 21 2315 41 98 144 171 181 166 109 32 4 0 0 2.5 4.5 11 17 21 23.5 25.5 26 94 152 195 211 162 56 6 0 Northwest Horizontal Surface 0 2.5 4.5 11 17 21 23.5 25.5 26 28 54 102 137 123 49 5 0 0 5 20 85 ifin 212 244 281 290. 281 244 212 160 R5 20 5 0 Table 5. Solar Radiation (Direct plus Sky) Impinging Against Several Orientations and a Horizontal Surface Walls Having For 45 Deg North Lalitude on August 1 Sun Time Northeast 4:25 5K 6:00 0 22 87 7:00 8:00 9 KM) 151 144 , 100 10:00 11:00 12:00 46 28 26 1:00 2:00 ; 3K)0 25.5 23.5 21 4:00 5KX) 6 KM) 17 12 5.5 7:00 3.5 ..... 7:35 - - 0 . INTEN sity of Solar Radiation, Btu per Sq Ft per Hour . East 0 20 99 192 237 199 153 94 26 25.5 23.5 21 . 17 12 5.5 3.5 0 Southeast 0 17 56 134 188 197 184 158' 116 63 23.5 21 17 12 5.5 3.5 .0 South 0 3.5 5.5 12 48 93 121 146 156 146 121 93 48 12 5.5 3.5 0 Southwes West . Northwes Horizontal Surface 00 3.5 3.5 5.5 5.5 12 12 17 17 21 21- 23.5 63 116 . 23.5' 25.5 26 158 94 184 153 197 199 188 > 237 134 192 . 56 99 0 3.5 5.5 12 .17 21 23.5 25.5 26 28 46 100 . 144 151 87 0 9 27-' 89 156 205 243; 259 281. 259 243 205 156 89 27 . 17 20 0 . 0, 22 9 0- - - 0 . CHAPTER 7. COOLINC LOAD. The variation in radiation intensity on differently oriented surfaces is . given in Fig. 1, and in Tables 2, 3, 4 and 5. The greater part of the radi ation intensity is always direct radiation from the sun. However, during the time when the sun is shining, any surface receives radiation of a lower intensity coming from all parts of the sky due to reflection and refraction. This scattered radiation intensity was found to vary from a very low value to values as high as 20 per cent of the total radiation observed on certain days in Pittsburgh. The curves and tables are for combined direct solar and scattered sky radiation, and are given to represent expected design radiation intensity for August 1.- They were prepared by the A.S.H.V.E. Laboratory from data1 obtained by pyrheliometer observations. A study of these curves discloses the periodic relationship and wide variation in solar intensity on various surfaces. It will be observed that Fig. 1. Solar Intensity Normal to Sun on Horizontal Surface and on Walls' for August 1 at 40 Deg North Latitude both the roof (horizontal surface) and south wall radiation curves are in exact phase relationship with each other, while those for the east and west walls overlap each other due to scattered sky radiation on the west wall during. the forenoon and on. the east wall during the afternoon. This phase relationship has an important bearing on the cooling load. Failure to consider the periodic character of heat flow resulting from diurnal movement of the sun and the lag due to heat capacity of the structure, which determine the timing and magnitude of the heat wave flowing through the wall, may result in a large error in load calculations. The values of solar intensity appearing in Fig. 1 must not be confused with the actual heat transmission through the wall, for much of the solar radiation impinging against the outer surface1 fails to pass through the wall. Instead it is delivered to the outside air by reflection, radiation, lA.S.H.V.E. Research Report No. 1147--Heat Gain Through Glass Blocks by Solar Radiation and Transmittance,'by F. C. Houghten. David Shore, H. T. Olson and Burt Gunst (A.S.H.V.E. Transactions, VoL 48. 1940, p. 83).